Abrasion resistant laminate and process for producing same

ABSTRACT

A laminated panel having an abrasion resistant surface is provided. The laminated panel includes a web being impregnated with a thermo-set resin, a bottom coat and an abrasion resistant top coat; a substrate; and thermo-fusing a bottom sheet to a second surface of the substrate opposite the first surface. The web is thermo-fused to one surface of the substrate, and the bottom sheet is simultaneously thermo-fused to the opposite surface of the substrate. A process for making an abrasion resistant laminated panel is also provided. The process includes the steps of partially impregnating a paper sheet or web with a thermosetting resin, drying it, coating the top side of the partially impregnated paper sheet or web with an abrasion resistant coat, simultaneously coating the bottom side of the paper sheet or web with a thermosetting resin composition, thermo-fusing the coated paper sheet or web to a first surface of a substrate and a bottom sheet to produce the laminated panel.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to decorative panels and, moreparticularly, to an abrasion resistant laminate for use as a decorativepanel. The abrasion resistant laminate is preferably a low pressurelaminate. The laminate has preferably a printed decorative pattern, butcan have a solid color. In addition, the present invention relates to aprocess for manufacturing such an abrasion-resistant laminated panel.

[0003] 2. Description of Related Art

[0004] Decorative panels have been used to produce kitchen and bathcabinets, office furniture, store fixtures and recreational furniture.For many years, decorative furniture components were made by laminatinga high pressure laminate to wood panel substrate, such as plywood orparticleboard. The glue line lamination occurred either before or afterthe furniture was assembled. Within the past twenty-five years, a lowpressure laminate has become available. Such low pressure laminates aremanufactured by directly laminating the decorative sheet to thesubstrate under heat and pressure.

[0005] Conventionally, high pressure decorative laminates have been madeby stacking and curing, under heat and pressure, a plurality of layersof paper impregnated with synthetic thermosetting resins. Normally, theassembly consists of three to eight core sheets. The assembly has fromthe base upward (1) phenolic resin impregnated Kraft paper, (2) a decoror decorative sheet impregnated with melamine resin, and (3) for printedpatterns, an overlay sheet which, in the laminate, is almost transparentand provides protection for the decor sheet.

[0006] Some improvements are described in U.S. Pat. Nos. 4,255,480 andU.S. Pat. No. Re. 32,152, both to Scher, et al. For example, U.S. Pat.No. 4,255,480 discloses manufacturing decorative laminates having anultra-thin, protective coating deposited as the uppermost layer of thedecor sheet to enhance abrasion-resistant properties. The decor sheet iscoated with an ultra-thin layer of a mixture of an abrasion-resistanthard mineral and a binder material. The hard mineral has a particle sizeof 20 to 50 microns.

[0007] Background patents of interest are U.S. Pat. Nos. 3,373,070 and3,373,071 to Fuerst. The Fuerst technique is to impregnate the decorsheet first with plain melamine resin, and then apply a thick coating tothe surface of the impregnated sheet using a relatively viscous mixtureof 2,000-60,000 centipoise.

[0008] U.S. Pat. No. 3,975,572 to Power employs an acrylicresin-melamine/formaldehyde resin composition which, like the coating inthe Fuerst patents, is applied over the already impregnated decor sheet,after the saturated decor sheet has been dried.

[0009] U.S. Pat. No. 4,322,468 to Raghava uses a special coatingcomposition of a fully hydrolyzed polyvinyl alcohol modifiedmelamine-formaldehyde resin.

[0010] U.S. Pat. No. 4,713,138 to Ungar et al. discloses a method ofproviding a paper facing sheet for use as the uppermost sheet in themanufacture of abrasion resistant decorative laminates. The processincludes the step of effecting coating and impregnating in essentiallyone step. According to this patent, the laminated panel has an abrasionresistant composition deposited in an ultra-thin layer.

[0011] U.S. Pat. No. 4,880,689 to Park et al., U.S. Pat. No. 4,940,503and U.S. Pat. No. 5,034,272 to Lindgren et al., U.S. Pat. Nos. 5,266,384and 5,702,806 to O'Dell et al., U.S. Pat. Nos. 5,288,540, 5,362,557,5,456,949 and 5,558,906 to Albrinck et al., and U.S. Pat. Nos.5,037,694, 5,093,185 and 5,037,694 to Ungar et al. all disclosedecorative laminates and/or processes for preparing decorativelaminates.

[0012] None of these patents disclose decorative laminates that haveabrasion resistant particles with an average particle size from about 9to about 12 microns and particle concentration of from about 2 to 4grams per square meter of surface area. Furthermore, none of thesepatents disclose a process, which involves simultaneously coating: (i)the top surface or side of a dried, partially impregnated paper with anabrasion resistant coat, and (ii) the bottom surface or side of thedried, partially impregnated paper with a thermosetting resin coating.Thus, none of these patents describe the efficient process andconstruction of the subject low pressure laminated panel.

SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a process forthe manufacture of a high quality, abrasion resistant laminated panel.

[0014] It is another object of the present invention to provide such aprocess in which the panel is preferably a low pressure laminated panel.

[0015] It is still another object of the present invention to providesuch a process that produces a printed decorative laminated panel or asolid color laminated panel.

[0016] It is a further object of the present invention to provide such aprocess that is less expensive due to less handling required by theprocess.

[0017] It is still further object of the present invention to providesuch a process that has simultaneous coating of the top and bottomsurfaces of a resin impregnated web.

[0018] It is yet a further object of the present invention to providesuch a panel in which particles are not applied in the dry state.

[0019] These and other objects of the invention are attained byproviding a laminated panel having an abrasion resistant surface. Theabrasion resistant panel comprises: a single, thermoset resinimpregnated web having a first surface and a second surface; an abrasionresistant top coat on the first surface of the thermoset resinimpregnated web; a bottom coat of a thermoset resin on the secondsurface, opposite the first surface, of the thermoset resin impregnatedweb; a substrate, wherein said substrate is thermally bonded to thethermoset resin impregnated web that is coated; and a resin impregnatedbottom or balancing sheet thermo-fused to said substrate on a surface ofsaid substrate opposite the bottom coat.

[0020] The above laminated panel having an abrasion-resistant surface ismanufactured by a process, comprising: (a) partially impregnating apaper sheet or web with a thermosetting resin, wherein said partialimpregnation is carried out so that about 40% to about 60% of the totalresin required for full saturation is used; (b) drying the partiallyimpregnated web to a volatile content from about 10% to about 15%,preferably from about 11% to about 13%; (c) coating the top surface orside of the dried, partially impregnated web with an abrasion resistantthermoset resin coat; (d) simultaneously coating the bottom surface orside of the dried, partially impregnated web with a thermosetting resincoat; (e) thermo-fusing the coated web onto a substrate; and (f)simultaneously thermo-fusing a resin impregnated bottom sheet to theother side of the substrate to produce a flat laminated panel. The resinimpregnated bottom sheet may be made pursuant to steps (a) through (d)above, or without the abrasion resistant coat.

[0021] During simultaneous coating of the top and bottom surfaces, theamount of coating resin used is controlled by metering the amount ofresin and abrasion resistant resin coat applied on each surface of theweb.

[0022] The laminated panel produced in accordance with the presentinvention has an improved abrasion and scratch resistance.

DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a side section view of a laminated panel of the presentinvention;

[0024]FIG. 2 is Table 1, which is the resin composition of the presentinvention;

[0025]FIG. 3 is Table 2, which is the abrasive mineral dispersion of thepresent invention; and

[0026]FIG. 4 is Table 3, which is the top coat of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring to the drawings and, in particular, FIG. 1, there isprovided a laminated panel of the present invention generallyrepresented by reference numeral 10. The laminated panel 10 includes asingle web 20, a top coat 30 on one surface of the web, a bottom coat 40on the other surface of the web, a substrate 50 thermo-fused to thebottom coat, and a bottom or balancing sheet 60 thermo-fused to thesubstrate on a surface of the substrate opposite the bottom coat. Thetop coat 30 and bottom coat 40 are thermoset resins that impregnate web20.

[0028] The substrate 50 can be made of wood, composite material, mediumdensity fiberboard, high-density board, particleboard or any otherwooden panel. Preferably, substrate 50 is made of particleboard.

[0029] The web 20 suitable for producing a resin impregnated web is afibrous material having pores sufficiently large for permittingpenetration of the impregnation resin therethrough. Preferably, web 20is derived from cellulose and/or modified cellulose. The web 20preferably is a single paper sheet or web.

[0030] The resin used to impregnate web 20 is a thermoset orthermosetting resin derived from an amino resin and, optionally, apolyol. The amino resin can be a monomeric, oligomeric, polymeric or amixture thereof. The amino resin can be formed by the reaction of anamino compound and an aldehyde, such as formaldehyde or glyoxal.

[0031] The amino compound is preferably selected from the groupconsisting of melamine, an N-substituted melamine such as N-methylmelamine, N,N′-dimethyl melamine and N,N′,N′′-trimethyl melamine, aguanamine derivative such as benzoguanamine and acetoguanamine, ethyleneurea, dihydroxyethylene urea, urea, a substituted urea such as an alkylsubstituted urea, a substituted guanidine and a mixture of any of thepreceding amino compounds. It is believed that it may be possible thatthe amino compound is a guanamine derivative such as cyclohexylcarboguanamine, glycoluryl, a substituted urea such as biuret, triuret,or guanidine.

[0032] Preferably, the amino resin is prepared from the reaction ofmelamine or urea with formaldehyde, and can be further partially orfully etherified with an alcohol of 1 to 4 carbon atoms. Thus, thepreferred amino resin can be a fully etherified, partially etherified orunetherified amino resin selected from the group consisting of amelamine formaldehyde resin, a urea formaldehyde resin and a mixturethereof.

[0033] The preferred thermosetting resin suitable for use with eachdifferent type of web 20, especially paper, is melamine formaldehyderesin. When a melamine formaldehyde amino resin is employed, the resinis prepared by combining formaldehyde with melamine in a ratio ofmelamine to formaldehyde from about 1:1.2 (melamine/formaldehyde) toabout 1:2.5.

[0034] The polyol suitable for use with the amino resin is a reactivecompound, such as a polyfunctional compound, having at least twohydroxyl groups or a group convertible thereto. The preferred polyol isselected from the group consisting of polyether polyol, polyhydricalcohol and mixtures thereof.

[0035] The resin compositions may further contain silanes. However,silanes are not preferred. The composition used for the top coat maycontain small quantities of an additive, such as a surfactant, toproduce uniform compositions and/or a solid lubricant to provide scuffresistance.

[0036] The abrasion resistant top coat or layer 30 is a resin containingan abrasion resistant hard mineral of fine particles. The fine particlesare dispersed in the amino resin mixture and are added to the web, butnot in dry form. The fine particles are in quantities sufficient toprovide an abrasion resistant layer without interfering with clarity.

[0037] The abrasion resistant particles are selected from the groupconsisting of alumina, silica and mixtures thereof. Preferably, theaverage particle size of the abrasion resistant particles is from about9 to about 12 microns. An example of a suitable abrasion resistantparticle is a mixture of alumina particles of about 9 and 12 microns. Inpractice, a calculated amount of the dispersion containing the particlesis added to the resin used in top coat 30 to yield about 2 to about 4grams per square meter of particles on the surface of web 20. Theabrasion resistant top coat 30 in the present invention is not anultra-thin layer.

[0038] The term “abrasion resistant coat” is used herein to denote acomposition or coat comprising abrasion resistant particles in thermosetresin. The abrasion resistant coat 30 is applied as a thin layer on onesurface of web 20, and has, as stated above, a concentration ofparticles from about 2 to about 4 grams per square meter of surfacearea. The laminated panel 10 also has a matte finish with a gloss meterreading about 10 to about 50 units. It is preferred that the gloss meterreading is about 15 to about 25 units.

[0039] The resin used as bottom coat 40 is preferably the same resin asthat of top coat 30. However, unlike top coat 30, bottom coat 40 doesnot have any abrasion resistant particles therein. The use of resinsystems other than amino resins in bottom coat 40 is also possible, butsuch use generally is not preferred.

[0040] The bottom coat 40 provides an interface between web 20 andsubstrate 50 through which the impregnated web and the substrate arethermally bonded in the thermo-fusing step.

[0041] The bottom on balancing sheet 60 is made of the same material asweb 20. Sheet 60 is also impregnated with a top coat and a bottom coat.The top coat of bottom sheet 60 may include one or more type of abrasiveresistant particles. The bottom coat of sheet 60 is made of the resinused in bottom coat 40. It should be noted that bottom sheet 60 may bethe same color or a different color than that of web 20.

[0042] The process of the present invention includes partiallyimpregnating web 20, such as a paper sheet, with the thermosettingresin. Partial impregnation is carried out so that only about 40% to 60%of the total resin required for full saturation is added. After thepartial impregnation step, impregnated web 20 is dried in an air floatoven to reduce the level of the volatile components and obtain animpregnated paper having a volatile content from about 10% to about 15%,and preferably about 11% to about 13%. The final mixture viscosityshould be low enough so that almost immediate saturation occurs aftercoating of web 20. Thereafter, the top or the exposed side of thepartially impregnated web 20 is coated with an abrasion resistant topcoat 30. This top coat is achieved by depositing on one surface, the topsurface, of web 20 a layer of the abrasion resistant top coat 30.Simultaneously, the other or bottom surface of web 20 is coated with thethermosetting resin to produce bottom coat 40. Simultaneous coating ispreferably carried out by metering the amount of resin and abrasionresistant coat applied on web 20 before and after each application.

[0043] When the thermosetting resin is a melamine formaldehyde resin,the resultant wet paper or web 20 is dried at an oven temperature fromabout 80° C. to about 180° C. This partial drying is carried out tofurther remove some of the volatile components and to partially advanceor cure the resin.

[0044] The coated web 20 is then thermo-fused onto substrate 50, bybottom coat 40 preferably at an applied pressure from about 250 to about450 pounds per square inch and a temperature from about 150° C. to about200° C.

[0045] The bottom or balancing sheet 60 is made by the same process asmaking web 20, except the resin for the top coat of bottom sheet 60 maynot have any abrasive particles therein. The bottom coat of bottom sheet60 is thermo-fused into a surface of substrate 50 opposite web 20, toproduce the abrasion resistant laminated panel 10 of the presentinvention.

[0046] The laminated panel 10 of the present invention is useful inproviding articles, which have an abrasion-resistant surface adapted towithstand extended use conditions without showing obvious signs ofwearing or deterioration.

[0047] The melamine formaldehyde resin, which is also called melamineresin in the present invention, is the conventional melamineformaldehyde resin that is used in the production of low pressurelaminates. The resin is manufactured from melamine crystal, formaldehydesolution, glycol, sugar, and water. The glycol is a plasticizer, whilethe sugar is used as an extender. All of these ingredients are chargedin a kettle. Polymerization is conducted under atmosphereic reflux andcontrolled alkaline pH. At the end of the reaction, the remainingadditives are added during cooling. After cooling, the pH of the resinmay be adjusted for storage.

[0048] Table 1 of FIG. 2 is the resin composition for the saturationstage and bottom coat. It includes melamine formaldehyde resin, ureaformaldehyde resin, glycol, preferably diethylene glycol, and at leastone catalyst. The catalyst used is one or more of the following: asolution of paratoluenesulfonic acid (PTSA) blocked with an amine orunblocked; methane sulfonate blocked with an amine; and phosphate ester.

[0049] Table 2, shown in FIG. 3, sets forth the ingredients and amountsof each ingredient that is in the abrasive mineral dispersion. Theingredients set forth in Table 2 are mixed in a vessel equipped with ahigh shear mixer until a stable dispersion is formed.

[0050] As set forth in Table 2 of FIG. 3, there is a certain amount ofpropylene glycol, the melamine formaldehyde resin and water. Inaddition, additives include a wetting agent, a defoamer, a firstdispersing agent, a second dispersing agent, a suspension agent andnatural cellulose fibers. The remaining additives may include alubricant and a chelating agent.

[0051] The wetting agent reduces surface tension. A preferred wettingagent is alkylphenol ester in a petroleum distillate.

[0052] The defoamer is intended to prevent formation of foam duringshearing. A preferred defoamer is a non-silicone.

[0053] The first dispersing agent is intended to prevent flocculation ofthe dispersed particles. It is preferred that the first dispersing agentis an ammonium salt of acrylic polymer. The second dispersing agent is athixotropic agent. It is preferred that the second dispersing agent isalkanolammonium salt of a polycarboxylic acid of low molecular weight.

[0054] The suspension agent prevents hard packing of the abrasiveparticles. Any conventional suspension agent that achieves this functioncan be used.

[0055] The NaOH 4N is used primarily to obtain a neutral pH. The naturalcellulose fibers preferably has a fiber length from about 15 to about 25microns.

[0056] Table 3, set forth in FIG. 4, sets forth top coat 30 of thepresent invention. Basically, top coat 30 has the melamine formaldehyderesin, the dispersion of particles set forth in Table 1, a releaseagent, and at least one catalyst, such as the catalyst of Table 1.

[0057] The release agent is used to prevent the panel from sticking tothe plate used in manufacturing. The release agent can be anyconventional release agent that does not affect the materials of thelaminate.

[0058] The following specific examples are provided to illustrate theprocess of the present invention.

EXAMPLE 1

[0059] A continuous paper web 20 is impregnated, to about 40% to about60% of the total resin required for full saturation, by dipping in asaturating bath containing the composition set forth in TABLE 1 of FIG.2. The melamine formaldehyde resin present in the composition isprepared by mixing the preferred melamine ingredients of the presentinvention. After saturation, the excess resin is squeezed out between apair of nip rolls at the end of the saturating bath. The paper web isthen dried in an air float oven to a volatile content from about 10% toabout 15%. The resin reaches a gel consistency so that resin applied inthe subsequent coating stages does not completely blend with the resinapplied in the saturation stage. A stable dispersion having the abrasiveresistant particles is prepared by mixing the ingredients set forth inTABLE 2 of FIG. 3 in a high shear mixer until a stable dispersion isformed. This can be prepared separately and stored until use, or it canbe prepared at this time. The abrasion resistant top coat 30 havingmelamine formaldehyde resin and the abrasive resistant particles, isthen prepared by mixing the abrasive resistant particle dispersion,melamine formaldehyde resin, a release agent and a catalyst Table 3. Ameasured quantity of the abrasion resistant top coat 30 is then appliedto the top surface of paper web 20. Simultaneously, the saturatingcomposition of Table 1 having melamine formaldehyde resin is applied asbottom coat 40 to the bottom surface of paper web 20 in an amountsufficient to prevent paper curling and to achieve strong thermo-fusionwith substrate 50. The treated web 20 thus formed is then dried to thedesired level of volatile content and stored for subsequent lamination.The treated web 20 is thermo-fused to a particleboard substrate 50 in aflat or a continuous double belt press at about 150° C. to about 200° C.temperature and about 250 to about 450 pounds per square inch pressure.The bottom sheet 60 is simultaneously thermally fused to substrate 50 toproduce a laminated panel in accordance with the present invention.

[0060] For a printed decorative laminated panel, the initial abrasionpoint (IP) of the decorative surface made with this technique is fromabout 100 to about 250 cycles as determined by the NEMA LD 3-1995 WearResistance Method. The Wear Resistance values are above 400 cycles forthe decorative surface prepared using the process of the presentinvention.

[0061] The present invention is used preferably to produce a printeddecorated laminate panel. However, the present invention may be used toprovide a solid color laminate panel.

[0062] While the method/process of the present invention is primarilydirected to low pressure laminates, it is believes that it can also beused to make high pressure laminates.

[0063] It will be obvious to those skilled in the art that variouschanges may be made without departing from the scope of the presentinvention and that the invention is not to be considered limited to whatis described and exemplified in the specification.

Wherefore we claim:
 1. A laminated panel having an abrasion resistantsurface, comprising: a single web having a first surface and a secondsurface, said single web being impregnated with a thermoset resin; anabrasion resistant top coat on the first surface of said web, said topcoat having the thermoset resin with a plurality of abrasive resistantparticles therein, wherein the abrasion resistant particle concentrationin said top coat is from about 2 to 4 grams per square meter; a bottomcoat of a thermoset resin, said bottom coat being impregnated in thesecond surface of said web; a substrate being thermos-fused to saidbottom coat of said web; and a bottom sheet being thermo-fused to asecond surface of said substrate opposite said bottom coat of said web.2. The laminated panel of claim 1, wherein the particle size of eachabrasion resistant particle is from about 9 to about 12 microns.
 3. Thelaminated panel of claim 1, wherein the substrate is a particleboard. 4.The laminated panel of claim 1, wherein the thermoset resin is derivedfrom: an amino resin; and optionally, a polyol having at least twohydroxy groups.
 5. The laminated panel of claim 4, wherein the aminoresin is an etherified or unetherified amino resin selected from thegroup consisting of a melamine formaldehyde resin, a urea formaldehyderesin and mixtures thereof.
 6. The laminated panel of claim 5, whereinthe polyol is selected from the group consisting of a polyether polyol,a polyhydric alcohol and mixtures thereof.
 7. The laminated panel ofclaim 1, wherein the abrasion resistant top coat comprises abrasionresistant particles selected from the group consisting of alumina,silica and mixtures thereof.
 8. The laminated panel of claim 1, whereinthe resin impregnated web comprises paper.
 9. A process formanufacturing a laminated panel having an abrasion resistant surface,comprising: partially impregnating a paper sheet with a thermosettingresin, wherein said partial impregnation is carried out so that about40% to about 60% of the total resin required for full saturation isused; drying the partially impregnated paper to a volatile content ofabout 10% to about 15%; coating the top surface of the partiallyimpregnated paper with an abrasion resistant coat; simultaneouslycoating the bottom surface of the partially impregnated paper with athermosetting resin coating, wherein said top and bottom surfacecoatings are carried out by metering the amount of resin and abrasionresistant coat applied on the paper; and thermo-fusing the coated paperonto a substrate; and simultaneously thermo-fusing a bottom sheet to asurface of the substrate opposite the coated paper to produce thelaminated panel.
 10. The process of claim 9, wherein the paper is a web.11. The process of claim 9, wherein the thermosetting resin comprises:an amino resin; and optionally, a polyol having at least two hydroxylgroups.
 12. The process of claim 9, wherein the abrasion resistant coathas abrasion resistant particles selected from the group consisting ofalumina, silica and mixtures thereof.
 13. The process of claim 12,wherein the average particle size of the abrasion resistant particles isfrom about 9 to about 12 microns.
 14. The process of claim 9, whereinthe laminated panel has the abrasion resistant particles from about 2 toabout 4 grams per square meter of surface area.
 15. The process of claim9, wherein the thermo-fusing step applies pressure from about 250 toabout 450 pounds per square inch.
 16. The process of claim 9, whereinthe thermo-fusing step has a thermo-fusing temperature from about 150°C. to about 200° C.
 17. The process of claim 9, wherein the substrate isa particleboard.
 18. The process of claim 9, wherein the substrate ismade of a material selected from the group consisting essentially ofwood, composite material, medium density fiberboard, high-density board,particleboard and mixtures thereof.
 19. The process of claim 9, whereinthe partially impregnated paper is dried to a volatile content fromabout 11% to about 13%.
 20. A laminated panel prepared by the process ofclaim 9.